ib chem past paper
•
The equilibrium law
DYNAMIC EQUILIBRIUM forward A +8
reaction
""r=====~'~ reverse reaction
Most chemical reactions do not go to completion. Once some products are formed the reverse reaction can take place to reform the reactants. In a closed system the concentrations
of all the
reactants and products will eventually become constant. Such a system is said to be in a state of dynamic equilibrium.
The forward and reverse reactions continue to occur, but at equilibrium the rate of the forward reaction is equal to the rate of the reverse reaction.
(ii)
(i)
Dynamic
2.0
2.0
7
E 1.8
-o
~ 1.6
N,O,(gl
=
E 1.8
-o
~ 1.6
2N02(gl
.~ 1.2
=
2N,O,(gl
~ 1.0
~1.4
25 v 0.6
back into liquid.
0.4
0.2
Equilibrium
rate of vaporization
0.6
0.4
molecules
in the
liquid will escape from the surface to become vapour and the slower moving molecules in the vapour will condense
80.8
0.8
also occurs when physical changes
the water vapour. The faster moving
~1.4 o .~ 1.2
~ 1.0
2NO,(gl
equilibrium
take place. In a closed flask, containing some water, equilibrium will be reached between the liquid water and
will be established
when the
equals the rate of condensation.
0.2
NO,
time
time
CLOSED SYSTEM
Graph (i) shows the decomposition of
N20.\" Graph (ii) shows the reverse reaction starting with NOr Once equilibrium is reached (sh-own by the dotted line), the composition of the mixture remains constant and is independent of the starting materials.
A closed system is one in which
the macroscopic properties remain constant. If the system is open some of the products from the reaction could escape and equilibrium
Examples
THE EQUILIBRIUM CONSTANT
Consider the following
general reversible
reaction
in which
w
moles of A react with x moles of B to form y moles of C and z moles of D. wA + x8
At
The equilibrium law
DYNAMIC EQUILIBRIUM forward A +8
reaction
""r=====~'~ reverse reaction
Most chemical reactions do not go to completion. Once some products are formed the reverse reaction can take place to reform the reactants. In a closed system the concentrations
of all the
reactants and products will eventually become constant. Such a system is said to be in a state of dynamic equilibrium.
The forward and reverse reactions continue to occur, but at equilibrium the rate of the forward reaction is equal to the rate of the reverse reaction.
(ii)
(i)
Dynamic
2.0
2.0
7
E 1.8
-o
~ 1.6
N,O,(gl
=
E 1.8
-o
~ 1.6
2N02(gl
.~ 1.2
=
2N,O,(gl
~ 1.0
~1.4
25 v 0.6
back into liquid.
0.4
0.2
Equilibrium
rate of vaporization
0.6
0.4
molecules
in the
liquid will escape from the surface to become vapour and the slower moving molecules in the vapour will condense
80.8
0.8
also occurs when physical changes
the water vapour. The faster moving
~1.4 o .~ 1.2
~ 1.0
2NO,(gl
equilibrium
take place. In a closed flask, containing some water, equilibrium will be reached between the liquid water and
will be established
when the
equals the rate of condensation.
0.2
NO,
time
time
CLOSED SYSTEM
Graph (i) shows the decomposition of
N20.\" Graph (ii) shows the reverse reaction starting with NOr Once equilibrium is reached (sh-own by the dotted line), the composition of the mixture remains constant and is independent of the starting materials.
A closed system is one in which
the macroscopic properties remain constant. If the system is open some of the products from the reaction could escape and equilibrium
Examples
THE EQUILIBRIUM CONSTANT
Consider the following
general reversible
reaction
in which
w
moles of A react with x moles of B to form y moles of C and z moles of D. wA + x8
At